We have shown that macrophages isolated from the testis respond to FSH while macrophages isolated from the peritoneal cavity do not. FSH stimulated protein and lactate secretion in a dose-dependent manner in vitro and in vivo. Unlike the effects of FSH Sertoli cells, the accumulation of intracellular protein by macrophages was unaffected by FSH. LH, insulin, testosterone, or estradiol had no similar effects. Macrophages obtained from the peritoneal cavity were not responsive to FSH. Most recently, we have obtained evidence that secreted products of macrophages influence testosterone secretion by cultured Leydig cells. Since it is not known if these two phenomena are causally related, the experiments of this proposal will be undertaken in two phases to evaluate this possibility. First, we will determine the molecular weights and isoelectric points of secreted proteins using two-dimensional polyacrylamide gel electrophoresis. These studies will allow us to compare the pattern of proteins secreted by macrophages with and without FSH treatment and from macrophages from various tissues. These studies will allow us to determine if the secreted proteins of testicular macrophages are different from those secreted by macrophages from other tissues and also provide information concerning the ability of FSH to increase the appearance of new proteins. We will also determine if these proteins have similar biological activities (lysozyme and collagenase activity) as those proteins known to be secreted by macrophages from other tissues. Finally, we will test the validity of our preliminary studies which indicated that macrophages are capable of influencing testosterone secretion by Leydig cells. The general chemical nature (heat stability, molecular weight, solubility in organic solvents and activity after charcoal stripping) of the putative secretory product(s) that macrophages produce that are responsible for influencing testosterone secretion in Leydig cells will be determined. We will also determine if FSH stimulates the secretion of this factor(s) and if the factor(s) is(are) capable of potentiating the effects of LH on Leydig cells.